The present invention generally relates to audio equipment, and more particularly, to an automatic noise reduction circuit.
While using audio equipment, for example, when audio sources are plugged into an audio mixer or amplifier, they can produce undesirable noise. In some cases, the noise may be prolonged and unnerving to listeners. For example, some audio connections can produce a low and agitating hum that can be distracting.
Some audio equipment such as audio amplifiers and audio mixers include ground-loop isolation circuits directly after the inputs so that the ground from an input device can be disconnected when unwanted ground plane noise is introduced into the amplified audio. In some cases, an audio circuit is designed so that a particular source and output device are contemplated and ground loop isolation circuits are then manually selected to adjust for the optimal noise level.
However, this approach may not account for the amplifier or mixer being difficult to reach or having numerous inputs. For example, in classroom or office settings, the amplifier or mixer may be located in the ceiling, another room or equipment rack, while the inputs are connected via an extended audio interface some distance away, perhaps mounted in the wall. In these situations, the audio amplifier of an audio system may be difficult to access, thus making the ground-loop isolation switches difficult to access. In addition, an audio system may have many inputs making ground-loop isolation selection complex and time consuming.
As can be seen, there is a need for a noise reduction circuit that can automatically and quickly detect the noise level of an audio connection and reduce the noise to desirable levels.